1. Field of the Invention
The present invention relates to cigarette making apparatus and a cigarette rod product and more particularly to a tobacco trimming apparatus for removing the surplus tobacco from a continuous stream or rod of cut tobacco on a cigarette maker and the cigarette rod product of such apparatus.
2. Description of the Prior Art
Modern cigarette makers utilize a trimmer disk/paddle wheel assembly in the formation of a rod or braid of cut tobacco that is subsequently formed into a cigarette rod. In the cigarette maker, a braid or bed of cut tobacco is continuously formed against a foraminous vacuum belt and the trimmer disk/paddle wheel assembly shears off portions of the tobacco braid or bed into a final continuous, elongated tobacco shape or profile. The tobacco is then wrapped in cigarette paper to form a continuous cigarette rod that is subsequently cut into appropriate lengths for making individual cigarettes. One example of such a cigarette maker is manufactured by Hauni Maschinenbau AG of Hamburg, Germany.
Typically, the trimmer disks of such cigarette makers have pockets or recesses formed in the periphery of the disks for the purpose of increasing the volume of cut tobacco at given intervals or spacing along the braid of tobacco. Because the final cigarette rod diameter is substantially constant along its length, the increase of tobacco volume at given intervals creates a more dense tobacco rod at those intervals. By cutting the rod at the areas of greater tobacco rod density or packing density, the tobacco rod at both the lit end and the filter end of a cigarette is of greater density than the density of the tobacco rod intermediate the cigarette ends. The greater rod density at the lit end reduces tobacco fallout at that end during processing and packaging of the cigarettes and the greater rod density at the filter end provides sufficient structure or body for attachment of a filter to the tobacco rod. The densification of the tobacco rod at the ends of the rod allow cigarette manufacturers to reduce the total weight of tobacco in a cigarette yet maintain an acceptable product quality as well as an acceptable reject rate in the cigarette maker.
In one example of a conventional trimmer disk, the pockets or recesses in the disk have a radial depth of about 3.0 mm and a circumferential width of about 22.0 mm with four or six pockets symmetrically spaced around the disk periphery. Since each pocket width spans two lit ends or two filter ends, this configuration theoretically provides a dense region of about 11.0 mm at each end of the cut tobacco rod. The number of pockets on the trimmer disk periphery is a function of the diameter of the disk and the length of the cigarette being manufactured, as well as the rotational speed of the disk and the longitudinal velocity of the tobacco braid.
It is known to provide a tobacco braid with alternating regions of different densities, i.e., so as to provide a cigarette rod having a greater density at the lit end and a lesser density at the filter end. U.S. Pat. No. 4,210,159 discloses a trimmer disk/paddle wheel assembly in which alternating pockets on the trimmer disk are formed with different depths so as to provide a greater cross-sectional area of tobacco at alternating pockets and thus a greater density of the tobacco rod at the location of the pocket with the greater depth. The widths of all the pockets are the same so that the lengths of the dense regions at each end of the rod are the same.
U.S. Pat. No. 5,526,826 discloses an alternative arrangement for densifying longitudinally spaced regions along a tobacco braid. In the arrangement of this patent, a compacting unit disposed upstream of a trimmer disk assembly comprises a rotating wheel with a plurality of equiangularly spaced peripheral lobes which compact longitudinally spaced apart regions of an advancing tobacco stream to densify the tobacco stream in those regions. Insofar as taught by U.S. Pat. No. 5,526,826, each of the densified regions of the tobacco braid formed by the lobed wheel is uniform both in density and length.
It has been discovered that one problem associated with the conventional trimmer disk/paddle wheel assembly as disclosed in the aforementioned U.S. Pat. No. 4,210,159 is that as the speed of the cigarette maker is increased from about 2000 rods/minute up to about 8000 rods/minute, the densification of the end regions gradually deteriorates resulting in reduced cut end quality and an increased rejection rate. Increasing the rod density at the cut end regions for a given weight of tobacco in a cigarette can improve end region quality at higher maker speeds, but is likely to result in a xe2x80x9csofterxe2x80x9d or less dense middle or intermediate region between the cigarette ends and creates the risks of rod breakage during manufacture and fire cone falloff during smoking.
It would therefore be desirable to provide a cigarette making apparatus that is capable of operating at speeds of up to about 8000 rods/minute to make a cigarette rod with no substantial deterioration of the end regions and a sufficiently dense intermediate region to avoid the problems of rod breakage during manufacture and fire cone falloff during smoking.
In view of the foregoing limitations and shortcomings of the prior art apparatus and cigarette rod product, as well as other disadvantages not specifically mentioned above, it should be apparent that there still exist a need in the art for a trimmer disk/paddle wheel assembly that provides the proper density distribution along the tobacco braid so that the cigarette maker can be operated at substantially higher speeds than is presently possible, i.e., up to 8000 rods/minute, with little or no sacrifice of quality at either end region or the intermediate region of the cigarette rod and no increase in tobacco weight in the cigarette. There is also a continuing need in the art to optimize the density profile of the tobacco blend with respect to rod formation dynamics at the higher cigarette maker speeds. There also exists a need for a cigarette rod product that has a unique density profile that makes it possible to increase the speed of the cigarette maker up to 8000 rods/minute with little or no increase in rejection rate of the product compared to the rejection rate at lower maker speeds.
According to both its apparatus and product aspects, the present invention fulfills that need by the use of an asymmetrical trimmer disk in a trimmer disk/paddle wheel assembly in which the pockets or recesses of the disk have different widths especially designed to provide an optimum density profile for a cigarette rod of a given tobacco weight. It is also contemplated according to the present invention that other asymmetrical configurations of the pocket widths may be used depending on the tobacco blend, cigarette rod length and weight of tobacco in the rod.
The asymmetrical trimmer disk of the present invention is provided with a plurality of pockets or recesses on its periphery in equiangularly spaced relation having alternating different circumferential or arcuate extent or width, that is, the width of every other recess is the same and the widths of adjacent recesses are different. This asymmetrical arrangement of the pockets or recesses advantageously provides a cigarette rod with a unique density profile with a longer, more dense region at the lit end of the cigarette rod and, at the filter end of the cigarette rod, a densified region that is shorter and less dense than the densified region at the lit end and an acceptable intermediate region between the densified end regions. In one non-limiting example of an asymmetrical trimmer disk according to the present invention, a four pocket trimmer disk for a 68 mm tobacco rod has two oppositely disposed first pockets with a depth of 4.0 mm and a width of 22 mm for forming the lit end of the rod and two oppositely disposed second pockets spaced 90 degrees from the first pockets with a depth of 3.0 mm and a width of 16 mm for forming the filter end of the rod. Pockets of the same dimensions may be used in a six pocket trimmer disk (three each of the first and second pockets above) to make 57 mm tobacco rods. Of course, other widths and depths of the asymmetrical trimmer disk may be used within the scope of the invention for other tobacco blends, cigarette rod lengths and weight of tobacco in the rod.
It has been found that operating cigarette makers using asymmetrical trimmer disks with the aforementioned pocket dimensions has resulted in significant improvement in loose ends of the tobacco rod and loose end rejects at higher maker operating speeds from 2000 rods/minute up to about 8000 rods/minute.
The cigarette rod product of the present invention has a density profile with a densified region at the lit end having a first density and a longitudinal length of about 11 mm and a densified region at the filter end having a second density less than the first density and a longitudinal length of about 8 mm.
With the foregoing and other advantages and features of the invention that will become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and the views illustrated in the drawings.